Method for manufacturing a plastic block bag

ABSTRACT

A bag of thermoplastics material is manufactured from a tubular foil by making one or two incisions from one end of the tubular foil having from the incision end edges partially aslant with respect to the longitudinal edges of the tubular foil. After unfolding the parts forming the bottom, the bottom flaps are inwards folded about a cross folding line situated between the folding line and the line extending perpendicularly to the longitudinal edges of the tubular foil. The foils are sealed together by applying heat to both sides of the stack of foils to be connected. If the seals are discontinuous a layer impermeable for solid substances and letting a gas through is provided. From the part forming the valve flap a V formed part may be removed. In order to improve the closure the part forming the valve flap may be subjected to stretching and/or provided with superficial incision resulting into a better flexibility of the treated part.

United States Patent 72] Inventor Jan Roeloi Jochem Hendrik DeVries Hardenberg, Netherlands [2]] Appl. No 866,427 [22] Filed Oct. 7, 1969 I45] Patented July 6, I97! (73] Assignee lndustriele Onderneming Wavin N. V.

Zwolle, Netherlands [32] Priority Oct. 10, 1968, Apr. 2, I969 3 3 Netherlands [3 1] 6,814,532 and 6,905,187

[ 54] METHOD FOR MANUFACTURING A PLASTIC BLOCK BAG 10 Claims, 15 Drawing Figs.

[52] 0.5. CI. 93/35 R, 93/8 VB, 229/57, 229/625 [5]] int. Cl B3lb49/04 [50] Field ofSearch..... 93/35 R, 35, 8 VB; 229/57, 58, 62.5

[56] References Cited UNITED STATES PATENTS 3,248,042 4/1966 Kasting et al. 93/35 R UX Primary lixammerBernard Stickney Alturney-lrving M. Weiner ABSTRACT: A bag of thermoplastics material is manufactured from a tubular foil by making one or two incisions from one end of the tubular foil having from the incision end edges partially aslant with respect to the longitudinal edges of the tubular foil.

After unfolding the parts forming the bottom, the bottom flaps are inwards folded about a cross folding line situated between the folding line and the line extending perpendicularly to the longitudinal edges of the tubular foil. The foils are sealed together by applying heat to both sides of the stack of foils to be connected.

lf the seals are discontinuous a layer impermeable for solid substances and letting a gas through is. provided. From the part forming the valve flap a V formed part may be removed. In order to improve the closure the part forming the valve flap may be subjected to stretching and/or provided with superfcial incision resulting into a better flexibility of the treated part.

PATENTED JUL 6 I971 SHEET 1 [IF 5 MTENTEUJUL 6|97i 3.590.688

1 sum 2 OF 5 PATENTEU JUL s :97;

SHEET 3 BF 5 PATENTED JUL 6 IQYI SHEET U [1F 5 PATENTED JUL 6|971 SHEET 5 OF 5 METHOD FOR MANUFACTURING A PLASTIC BLOCK FAG The invention relates to a method for manufacturing a plastic bag, whether or not provided with a filling valve, from a tubular foil by making from one end of the tubular foil at least one incision whilst formirig a first corner flap between the longitudinal incision and the longitudinal edge of the tubular foil which is nearest thereto, whereupon the bottom flap portion situated on the other side beside the longitudinal incision are folded outwards about a folding line extending in the tubular foil portion next to the point of incision, and folding inwards the bottom flaps about a transverse folding line situated between the folding line and the line extending perpendicularly to the longitudinal edges of the tubular foil and through the end point of the longitudinal incision and making connec tions in order to connect the bottom flap portions.

Many methods for manufacturing such types of plastic bags are known. These bags have however the drawback that rather much material is required in order to obtain the desired strength of the bottom of the bag or the seals produced in such bags are not strong enough.

It is an object of the invention to provide a method for such a plastic bag with a very strong sealed bottom which even in particular cases is achieved whilst saving material. This object is attained according to the invention in the way that the starting point is a tubular foil wherein the end edges of the bottom flap portions situated beside the incision extend, at least from the incision, partially aslant with respect to the longitudinal edges of the tubular foil, and the bottom flap portions are inwards folded about a crossfolding line situated between the folding line and the line extending perpendicularly to the longitudinal edges of the tubular foil through the end point of the longitudinal incision whilst folding back triangular portions of the second corner flap, situated beside the crossfolding line, under the remaining portion of the comer flap, preferably the seals are obtained by applying heat to both sides of the seals of the bottom to be formed.

Due to this feature material can be saved and a very strong bottom formed as a result of the sealed or glued connections extending obliquely therein. Supply of heat to both sides will result in a very excellent seal.

The invention will hereinafter be clarified with reference to the drawing in which a number of embodiments are represented.

In the drawing:

FIG. I is a flattened part of a tubular foil used for manufacturing a bag;

' FIG. 2 is a tubular foil according to FIG. ll after folding the comer flaps;

FIG. 3 shows a sealed bottom of a bag obtained from a tubular foil portion according to FIG. i;

FIG. 4 shows a modified embodiment of the sealed bottom of the bag according to FIG. 1;

FIG. 5 shows a flattened part of a tubular foil provided with two longitudinal incisions;

FIG. 6 shows a part of a tubular foil according to FIG. 5 in the unfolded position;

FIG. 7 shows a bottom of a bag obtained after making seals in the bottom of the back formed from the tubular foil according to FIGS. 5 and 6;

FIG. 8 shows the way in which a tubular foil according to FIG. 5 is cut from a very long tubular foil;

FIG. 9 shows a flattened tubular foil portion with two longitudinal incisions and two comer flaps of dissimilar length, the end edges of the bottom flaps extending aslant with respect to the longitudinal edges of the tubular foil;

FIG. 10 shows a part of the tubular foil according to FIG. 9 in an unfolded situation, and

FIG. 11 shows a sealed bottom of a bag of a tubular foil portion according to FIG. 9 obtained after folding the bottom flaps and providing the sealed connections,

FIG. 12a and 12b sections of the bottom of a plastic bag and a stretched or superficially incised valve, before and after filling the bag;

FIG. 33 a device for stretching a valve;

FIG. M a sealing and separating device as used for forming a bottom.

In FIG. I a flattened tubular foil portion 1 with longitudinal edges 2 and 3, a front wall 4 and a backwall 5 is represented. The end edges 6 and 7 of the front and backwall 4 and 5 extend aslant with respect to the longitudinal edges 2 and 3 of the tubular foil. A longitudinal incision 8 is provided in the walls d and 5 of the tubular foil 1, the incision terminating in the end point 9 of the incision.

The part 1 of the tubular foil is unfolded by folding the front and backwall t and 5 about a folding line 16) which extends in the portion of the tubular foil situated outside of the longitudinal incision d.

On folding the foil a valve 11 is formed which on the longitudinal edge 3 ends in an intersection 10! while on the other side of the tubular foil a triangular face 12 is formed. Also the bottom flaps Ma, Mb are formed.

Thereupon folding is effected about the crossfolding lines I311 and 13b which extend substantially perpendicular to the longitudinal edges 2 and 3 of the tubular foil and lie between the end point 9a, 9b of the incision and the folding line 10. After folding inwards the bottom flaps 14a and 14b about the crossfolding lines 13a and 13b the bottom flaps 143a and 14b are again folded back. From the triangular face 12 a triangle 112a, defined by the lines I5, I7 and 20 is folded under the portion of the triangular face 12, which constitutes the comer flap Zll, whereby the triangle 112b, defined by the lines 20, 16b and 17 comes to lie simultaneously under the triangle 12a. The same is done with the triangle defined by the lines l7, l8 and I9 and the triangle 1l2d defined by the lines 16a, 17 and 19. On performing these operations the corner flaps 14a and Mb are again folded over one the other, whcreuponthese comer flaps, after providing a separating means (see FIG. 14)

between the bottom flaps 14a, 14b and the valve situated thereunder and the walls 4 and 5 of the tubular foil are sealed or glued. Hereby the sealed joints Z2 and 23 are formed by sealing the end edges 7 to the bottom flap Ma, the end edges 6 to the bottom flap 14b, respectively. Also end edges 15 and 18 are sealed to the bottom flaps Ma, 14b and the end edges 8a, 8b of the valve opening, are connected by sealing or glueing.

Instead of sealing the edges 15 and 18 to the bottom flap 14a, Mb it is also possible according to FIG. 4, after having formed the bottom flaps to fold back the triangular unit comprising triangle iZa, 12c and a triangle defined by the lines l5, l8 and 24 and to connect the edges 15, 18 and 24a (by sealing or glueing) and the edges 16a and l6b. Although this bag is slightly less strong it is advantageous in that aeration channels are easily obtained in the way that the seals are not provided on but beside the edges l5, 18.

The aforementioned bag may be manufactured in an inexpensive way since on blanking out already a tubular foil portion with aslant extending end edges 6 and 7 may be directly obtained without the formation of waste, the material being completely converted into a bag. Due to the inclined edges 6 and '7 a very strong sealed bottom is obtained with less material than in case of straight edges.

An important embodiment is distinguished in that instead of continuous sealed joints 22, 23 same are discontinuous, while also second likewise discontinuous sealed joints 22a and 23a are provided. In this way a proper deaeration is always possible since the air in the bag can easily escape between the sealed joints. If desired a foam plastic or nonwoven material 24 can be provided between the sealed joints 22 and 22a, 23 and 230, or 220 and 23a, respectively in order to prevent solid substance from disappearing through these openings.

In the FIGS. 5 to 8 is likewise started from a tubular foil portion I with slanting end edges 6 and 7, a front and backwall 4 and 5 and an incision 8 with end point 9 whilst forming a first corner flap Ill, but on the other hand at some distance from the longitudinal edge 2 is also provided an incision ending in the point 26, the connecting line 27 between the end points 9 and 26 of the incisions extending almost perpendicularly to the longitudinal edges 2 and 3 of the tubular foil. Unfolding is here likewise effected about the folding line it) situated in the area of the tubular foil portion next to the connecting line 27 whereby corner flaps ll, 29, and bottom flaps 114a, Mb are formed.

Thereupon the bottom flaps Ma Mb are folded together with a portion of the comer flaps 11 and 29, about the line 13a, 13b extending in the area next to the connecting line 27 and at a short distance thereof. The end edges 29a, 2% come to lie under the corner flaps.

Finally the sealed joints 23 and 22' according to the original end edges 6 and 7 of the bottom flaps and the welded joints [5' and 18 are provided.

This bag is very suitable for the purpose of manufacturing plastic bags whilst using small quantities of material, the

strength being considerable since due to the slanting end edges 6 and 7 a very firm welded joint can be obtained which can take a considerable load. So it appears from FIG. 8 that by means of suitable cutters the incisions 3 and the end edges 6 and 7 can be provided at a time without waste of tubular foil material.

In H68. 9 to 11 another embodiment is represented in which exclusively the end edges of the bottom flaps Ma and 14b are inclined with respect to the longitudinal edges 2 and 3 of the tubular foil. Due to the incisions 8 and 25 with their end points 9, 26, respectively the corner flaps ll, 29 and the bottom flaps 14a" and 14b" are formed on unfolding about the line it). Also the end points 911, 912, 26a and 26b of the incisions are obtained. Thereupon folding about the line 13a, 13b is effected whilst forming the bottom of the bag. The corner flap l l' constitutes a valve due to the provision ofa separating means with heated seal wires 42, 42' between the corner flap 11'' and the bottom flaps Ma", Mb" situated thereabove.

The desired bag fitted with a valve is obtained due to the provision of the welded joints 33, 34 according to the end edges 6 and 7, and the sealed joint 32 in the vicinity of the end edges 25a, 25b and the edges 84, 8b of the incisions 8.

A triangular portion 30 of the corner flap 29' beside the incision 25 can be efficiently removed whilst forming a corner flap edge 35.

The corner flap 11" of the bag is longer than the corner flap 29', while the bottom flaps Ma", Mb" are shorter than the corner flap 11", but longer than the corner flap 29'.

It should be noted as comparison that the quantity of material required for the botton'l of a particular bag according to the embodiment of FIG. 9 is 1540 cm? gross, while 1364 cm. net thereof is effectively worked up in the bottom, the cuttings can obviously be used again. in the embodiment according to FIG. 5, l 155 cm. gross is required which completely and effectively are worked up in the bottom.

As valves having right ends are not preferable in case of filling said bags with coarse hard materials, involving the use of short filling tubes of the filling machines, it is recommended to remove a part 42 from valve 11". This will result in a valve having a V form.

On using thick foil material the part serving as a filling valve in the bag has difficulty in adapting itself to the bottom so that no desired adequate closure is guaranteed. This drawback may be removed by subjecting part 11' to a cross stretching action and/or is provided with superficial lines of incision 36. As a result thereof the valve part ll' becomes more flexible. It is specially advisable to subject the end part 36 of the flap 11" to a cross-stretching treatment so that said end part 36 becomes thinner and adapts itself better to the bottom 37, while moreover when filling material presses against the flap part 36 channels 38 remain between part 36 and bottom 37, connecting the mouth of the valve and the interior of the bag.

The stretching and or the provision with superficial incision lines may be effected by means of a member consisting of clamping members 39 and two parts provided with toothing 40 and 41. On moving the toothings toward one the other the plastic material of valve portion 36 will be stretched.

it is also possible to provide simultaneously on stretching the foil material with superficial lines of incision. For that purpose the toothing may for instance have a sharp edge, however in such a way that exclusively superficial incisions are formed and the material is not cut through.

The superficial incisions of the surface of the foil may also be provided by means of cutters, which only very superficially touch the surface of the foil.

The sealed joints 32, 33 and 34 (and all other joints if necessary) are obtained by means of a separating member 44 (with sealing bars 44a, 44b and 44c (FIG. 14) and a sealing member 43 (with sealing bars 43a, 43b and 430).

Sealing member 43 and sealing member 44 are hingedly connected. After providing the separating member between the valve and the bottom flaps situated thereabove, or between the bottom flaps together with corner flaps and the walls of the bag. By heating sealing bars 43a-c and sealing bars 44ac heat is supplied to both sides of the layers forming the bottom resulting into excellent seals e.g. 32, 33, 34.

What I claim is:

l. A method for manufacturing a plastic bag, whether or not provided with a filling valve, from a tubular foil by making from one end of the tubular foil at least one incision whilst forming a first corner flap between the longitudinal incision and the longitudinal edge of the tubular foil which is nearest thereto, whereupon the bottom flap portions situated on the other side beside the longitudinal incision are folded outwards about a folding line extending in the tubular foil portion next to the point of incision, and folding inwards the bottom flaps about a transverse folding line situated between the folding line and the line extending perpendicularly to the longitudinal edges of the tubular foil and through the end point of the longitudinal incision, and making connections in order to connect the bottom flap portions wherein the starting point is a tubular foil wherein the end edges of the bottom flap portions situated beside the incision extend, at least from the incision, partially aslant with respect to the longitudinal edges of the tubular foil, and the bottom flap portions are inwards folded about a crossfolding line situated between the folding line and the line extending perpendicularly to the longitudinal edges of the tubular foil through the end point of the longitudinal incision, whilst folding back triangular portions of the second corner flap situated beside the crossfolding line under the remaining portion of the comer flap.

2. A method according to claim 1, wherein the starting point is a tubular foil provided with two longitudinal incisions in the vicinity of the one, the second longitudinal edge of the tubular foil, respectively the end edges of the bottom flaps extending aslant at least between the longitudinal incisions.

3. A method according to claim 1, wherein the first and second corner flap have a different length, the bottom flaps are shorter than the corner flaps and the end edges of the bottom flaps extend aslant from the longer corner flap to the shorter corner flap while the length of the bottom flaps is reduced as contemplated from the line constituting a connection between the end points of the incisions.

4. A method according to claim I, wherein beside one of the two longitudinal incisions a portion of the first and/or second comer flap is severed whilst forming a triangular recess so that a second edge of the corner flap is obtained.

5. A method according to claim 1, wherein the welded or glued joints which may consist of one or more partially interrupted sealed joints obtained by applying heat to both sides of the stack of foil layers to be connected.

6. A method according to claim ll, wherein a layer impermeable for solid substances and letting a gas through is provided between the discontinuous sealed joints.

7. A method according to claim 1, wherein if an incision is available after folding about the crossfolding line of the bottom flap portion the corner flap portion of the second bottom portions, the remaining portion of the comer flap is connected l 0 with the corner flap.

9. A method according to claim 1, wherein a V formed valve is obtained by removing a triangular end part from the corner flap and/or the valve.

10. A method according to claim 1, wherein the flap part serving as a valve at least at the end of the bottom flap is subjected to a cross stretching treatment and/or is provided with superficial lines of incision. 

1. A method for manufacturing a plastic bag, whether or not provided with a filling valve, from a tubular foil by making from one end of the tubular foil at least one incision whilst forming a first corner flap between the longitudinal incision and the longitudinal edge of the tubular foil which is nearest thereto, whereupon the bottom flap portions situated on the other side beside the longitudinal incision are folded outwards about a folding line extending in the tubular foil portion next to the point of incision, and folding inwards the bottom flaps about a transverse folding line situated between the folding line and the line extending perpendicularly to the longitudinal edges of the tubular foil and through the end point of the longitudinal incision, and making connections in order to connect the bottom flap portions wherein the starting point is a tubular foil wherein the end edges of the bottom flap portions situated beside the incision extend, at least from the incision, partially aslant with respect to the longitudinal edges of the tubular foil, and the bottom flap portions are inwards folded about a crossfolding line situated between the folding line and the line extending perpendicularly to the longitudinal edges of the tubular foil through the end point of the longitudinal incision, whilst folding back triangular portions of the second corner flap situated beside the crossfolding line under the remaining portion of the corner flap.
 2. A method according to claim 1, wherein the starting point is a tubular foil provided with two longitudinal incisions in the vicinity of the one, the second longitudinal edge of the tubular foil, respectively the end edges of the bottom flaps extending aslant at least between the longitudinal incisions.
 3. A method according to claim 1, wherein the first and second corner flap have a different length, the bottom flaps are shorter than the corner flaps and the end edges of the bottom flaps extend aslant from the longer corner flap to the shorter corner flap while the length of the bottom flaps is reduced as contemplated from the line constituting a connection between the end points of the incisions.
 4. A method according to claim 1, wherein beside one of the two longitudinal incisions a portion of the first and/or second corner flap is severed whilst forming a triangular recess so that a second edge of the corner flap is obtained.
 5. A method according to claim 1, wherein the welded or glued joints which may consist of one or more partially interrupted sealed joints obtained by applying heat to both sides of the stack of foil layers to be connected.
 6. A method according to claim 1, wherein a layer impermeable for solid substances and letting a gas through is provided between the discontinuous sealed joints.
 7. A method according to claim 1, wherein if an incision is available after folding about the crossfolding line of the bottom flap portion the corner flap portion of the second bottom flap situated beside the end portion of the folding lines are folded about the folding line and connected with the wall of the tubular foil by providing sealed joints on or in the vicinity of the outer edges of the second corner flap and the folding edges of the second corner flap.
 8. A method according to claim 1, wherein an incision has been provided and after folding the bottom flap portions about the crossfolding line and folding back the triangular portions, the remaining portion of the corner flap is connected with the corner flap.
 9. A method according to claim 1, wherein a V formed valve is obtained by removing a triangular end part from the corner flap and/or the valve.
 10. A method according to claim 1, wherein the flap part serving as a valve at least at the end of the bottom flap is subjected to a cross stretching treatment and/or is provided with superficial lines of incision. 